In large-scale manufacturing of digital-to-analog converters (DACs), integrated circuits having DACs are typically tested for compliance against design specifications. Some tests apply a signal to the DACs and monitor the outputs using expensive testing equipment, such as highly-calibrated testing DACs. The testing equipment, long test times, and limited multi-site testing capability contribute to high test costs.
A traditional test technique includes measuring the output voltage of the DAC under test for each of multiple digital input codes. The input codes may take the form of a digital ramp wave to measure intrinsic parameters of the DAC such as integral non-linearity, differential non-linearity, gain, and offset. The input codes may also take the form of a digital sine wave to measure transmission parameters such as signal-to-noise ratio, total harmonic distortion, and spurious free dynamic range. The testing equipment digitizes the output voltage of the DAC under test, performs a Fast Fourier Transform (FFT) on the digitized signal, and calculates the test parameters from the FFT. If the DAC under test does not meet minimum performance requirements, the DAC, or the part including the DAC, is discarded. Discarding parts reduces the yield from a manufacturing lot and increases associated costs. Therefore, discarding parts is to be avoided as much as possible.